/Engine/Source/Runtime/AIModule/Classes/BehaviorTree/BTFunctionLibrary.h
Resets indicated value to "not set" value, based on values type
static void ClearBlackboardValue ( [UBTNode](API\Runtime\AIModule\BehaviorTree\UBTNode) * NodeOwner, const [FBlackboardKeySelector](API\Runtime\AIModule\BehaviorTree\FBlackboardKeySelector) & Key )